A known valve timing control apparatus for an internal combustion engine is disclosed in U.S. Pat. No. 6,382,157B1 (see columns 5-10, FIGS. 4, 11). As illustrated in FIG. 11, the disclosed valve timing control apparatus 101 includes an outer rotor 105, an inner rotor 104, advanced angle chambers 161a, retarded angle chambers 161b, and a lock member 163a. The outer rotor 105 is synchronously rotatable with a crankshaft of an engine and having plural shoes 155 inside thereof. The inner rotor 104 is fixed to an end portion of a camshaft of the engine and having plural vanes 144 at outside thereof. Further, the inner rotor 104 is provided in the outer rotor 105 and is relatively rotatable with the outer rotor 105. The advanced angle chambers 161a and the retarded angle chambers 161b are formed between the plural vanes 144 of the inner rotor 104 and the plural shoes 155 of the outer rotor 105. The lock member 163a locks the inner rotor 104 at a predetermined angle relative to the outer rotor 105. The outer rotor 105 is provided with plural projections 182 at outer circumference thereof in regular intervals. Each projection 182 protrudes outwardly in a radial direction of the outer rotor 105. Further, the projection 182 allows an engagement of a chuck tool of an automatic machine used for an auto-assembly work.
With the configuration of the valve timing control apparatus 101 disclosed in U.S. Pat. No. 6,382,157B1, the outer rotor 105 is turned in a clockwise direction in FIGS. 11-12 by means of the chuck tool of the automatic machine, and the vanes 144 of the inner rotor 104, which are fixed at a most retarded angle relative to the outer rotor 105, are firmly contacted with the shoes 155 of the outer rotor 105. Accordingly, even when a clearance is left between the lock member 163a and an engaging hole 163b into which the lock member 163a is inserted, the disclosed valve timing control apparatus 101 can restrain an assembling error caused by the clearance.
Further, U.S. Pat. No. 6,382,157B1 also discloses a valve timing control apparatus, which is provided with a polygonal portion 184 at an inner surface of a concave seat 183 used for seating a fixing member, by which the inner rotor 104 is fixed to the camshaft, as illustrated in FIG. 12. As well as the projection 182, the polygonal portion 184 allows the engagement of the chuck tool of the automatic machine used for the auto-assembly work.
With the configuration of the valve timing control apparatus disclosed in U.S. Pat. No. 6,382,157B1, an angle of the inner rotor 104 relative to the outer rotor 105 can be held in order to prevent the inner rotor 104 from being turned in the clockwise direction in a condition where the outer rotor 105 is turned in the clockwise direction. Accordingly, the inner rotor 104 can be fixed at the most retarded angle phase relative to the outer rotor 105.
With the configuration of the valve timing control apparatus 101 disclosed in U.S. Pat. No. 6,382,157B1, the vanes 144 of the inner rotor 104 are firmly contacted with the shoes 155 of the outer rotor 105 by applying a load to the outer rotor 105 to rotate in a predetermined direction while holding the angle of the inner rotor 104 when the valve timing control apparatus 101 is mounted to the camshaft. Accordingly, the clearance between the lock member 163a and the engaging hole 163b is biased in one direction, and the assembling error caused by the clearance is thereby restrained.
Therefore, during mounting operation, the lock member 163a, the engaging hole 163b, the vanes 144 of the inner rotor 104, and the shoes 155 of the outer rotor 105 are applied with an excessive share load, which is unlikely applied to them during normal operation of the engine. Accordingly, strength of each component of the valve timing control apparatus 101 such as the lock member 163a, the vanes 144, or the like, may necessarily be increased only for the mounting operation. In consequence, the apparatus may occasionally be increased in size and weight.
A need thus exists for a valve timing control apparatus, which can be reduced in size and weight by reducing an unnecessary load applied to an inner structure thereof at the time of mounting operation relative to the camshaft.